The interaction of high-power lasers with solids generates an ionised material - a plasma. Such plasmas are being studied in laboratory experiments worldwide for a variety of reasons. Beyond this fundamental interest in the nature of plasmas is the possibility that laser-plasmas may lead to technological breakthroughs of significant importance. Foremost amongst these possible technologies is using laser-driven plasmas as a source of energy via fusion. Fusion offers the prospect of limitless energy with near zero carbon emission and no long-lived radiative waste. This would revolutionise the world energy markets and potential secure a base load energy supply for the UK independent of imports. Additionally maintaining a UK lead in this field also would allow UK high-tech industries to profit from involvement in fusion science.

The National Ignition Facility (NIF) in the US is making significant progress towards the goal of laser-driven fusion and a similar size facility in France, the LaserMegaJoule (LMJ), will soon be completed. Alternative approaches to laser-driven fusion are being pursued in Japan, France, UK and USA. Worldwide this represents billions of dollars of investment. UK plasma scientists have maintained a leading international role in these theoretical and experimental developments. In order to maintain that roll the UK needs to be internationally competitive in both theory and experiments. However to field experiments on NIF or LMJ the design of the experiment, laser configuration, target properties and diagnostics must all be simulated first. This requires a special form of fluid simulation code called a radiation-hydrodynamics code. Such codes model the properties of the fluid-like plasma and, crucially, the energy transported through the plasma via the strong electromagnetic radiation field resulting from the laser, plasma compression and heating. UK academia has no such code and is in danger of loosing its international lead as a result. This proposal is to develop a radiation-hydrodynamics code (Odin) capable of designing fusion pellets, diagnostics and advance fusion ignition schemes.

The type of radiation-hydrodynamics code that is needed for fusion research would be based around an scheme called Arbitrary Lagrangian Euler (ALE). Developing the Odin ALE code is a major undertaking. Odin would also have direct applications to other branches of laser-plasma physics. There are experiments being run, and planned, which aim to generate proton and carbon beams for medical treatments. Such ion-beam therapy is possible now but the potential exists to reduce the cost and size of equipment needed and have more control. Crucial to optimising such laser accelerators is an understanding of the plasma that first forms in front of the target before the main laser pulse arrives. This so called pre-plasma cannot be easily measured experimentally but it could be accurately simulated by the Odin code. Thus Odin would directly contribute to research in laser-plasma based proton accelerators. Pre-plasmas are also a serious issue for very high-power laser experiments, such as the EU funded Extreme Light Infrastructure (ELI), which aim to access the QED-plasma regime.

The Odin code will be used for decades by UK researchers. It is therefore essential that this code is sustainable and adaptable to the emerging hardware in high-performance computing. Computer scientists, as well as plasma physicists, will therefore collaborate in the development of the Odin code to ensure it is optimised for current and next generation computers and benefits from the advances in both physics and computer science. The UK Computational Collaborative Project in Plasma Physics (CCPP) will manage the whole project and the code made available to all UK based plasma researchers.

Potential Impact:
The underlying driver for all of this proposed work is that a community radiation-hydrodynamics code will enable the applications of laser-plasma physics to be realized. Hence in contrast to the academic benefits, which are largely dependent on how academics work and what would be available to them, here the impacts are simply the expected impacts from laser-plasma derived technology. These are:

- A laser driven fusion reactor, so called inertial fusion energy (IFE). If successful this would change the world's energy markets, ensure energy security for the UK and allow high-tech UK industry to be involved in the technology for IFE.

- Lasers are been actively studied as a source for high-energy particle beams. Protons or carbon beam therapy could therefore be improved in both energy range and cost efficiency with such a system.

- By maintaining the computational and high-energy density physics research base of the UK it would impact AWE's ability to maintain its support for the defense of the UK.